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Car Forum / Driving, Maintenance, Tuning / Car Audio / April 2004Stiffening Cap
I have a small .5 farad cap left over from a small sub I took out of my old Honda. I want to add a small sub and this cap into another car. The cap worked fine, it was just that I seemed to have to charge the thing periodically, for dumb things I did. Like leave the lights on, dome light on, etc and I was wondering if there would be a way to isolate a cap (with a relay perhaps) to avoid this. It would be necessary now because my new install will put the cap in an inaccessable area (behind a plastic side panel). Can anyone help me with this? If you run your car battery AND the CAP down you never should need to charge the cap seperatly... Jump starting the car will instantly charge the cap! So the cap does not need to be accessable to charge seperatly... Eddie Runner http://www.imlforum.com > I have a small .5 farad cap left over from a small sub I took out of > my old Honda. I want to add a small sub and this cap into another car. [quoted text clipped - 5 lines] > inaccessable area (behind a plastic side panel). Can anyone help me > with this? > I have a small .5 farad cap left over from a small sub I took out of > my old Honda. I want to add a small sub and this cap into another car. [quoted text clipped - 5 lines] > inaccessable area (behind a plastic side panel). Can anyone help me > with this? I don't understand what you're asking. You don't need to "recharge" your cap. The only time where I could see this being an issue is if you replace your battery. Even then, I wouldn't worry about it, especially with a 0.5F. > I don't understand what you're asking. You don't need to "recharge" your > cap. The only time where I could see this being an issue is if you replace > your battery. Even then, I wouldn't worry about it, especially with a 0.5F. Ok, If you drain your battery and you have a cap if nothing is isolating the cap from the system when you recharge the battery and power up your system it will at least blow the fuse to your cap, cause it draws way to much for a 10-20 amp fuse to handle. So I want to design a circuit to isolate the cap from the rest of my electrical system. Like I was thinking a relay attached to the remote turn on line from the HU to trigger the relay for the big wire, that would (I think) isolate the cap in case of drainage of the system. Does anyone know if this will work, or am I way off. Thanks The cap isn't electrically connected to your charging system and battery all the time? I've never heard of a system that would charge the battery and not the cap. Do you draw power for your sub amp from an accessory position on your fuse panel? However you have things connected, you can isolate your cap with a large diode. This will cause a small voltage drop (~1volt) which is significant in a car where you only have 12-14 volts to begin with. You should know though, a cap will slowly discharge on it's own if left unconnected for long periods of time. Leakage currents in the cap (and other components connected to it) are to blame. Your best bet in my opinion would be to permanently wire your cap to the battery, through a fuse of course. That way there are no complications from charging or discharging the system. > > I don't understand what you're asking. You don't need to "recharge" your > > cap. The only time where I could see this being an issue is if you replace [quoted text clipped - 9 lines] > think) isolate the cap in case of drainage of the system. Does anyone > know if this will work, or am I way off. Thanks > > I don't understand what you're asking. You don't need to "recharge" your > > cap. The only time where I could see this being an issue is if you replace [quoted text clipped - 4 lines] > power up your system it will at least blow the fuse to your cap, cause > it draws way to much for a 10-20 amp fuse to handle. No, it generally doesn't. Especially not a small 0.5F or 1F cap. This is partly because the current draw is transient and partly because it's rare for even a "dead" battery to produce no voltage. > So I want to > design a circuit to isolate the cap from the rest of my electrical > system. Like I was thinking a relay attached to the remote turn on > line from the HU to trigger the relay for the big wire, that would (I > think) isolate the cap in case of drainage of the system. Does anyone > know if this will work, or am I way off. Thanks Relay or not, the cap would still have to charge once the relay was switched. If you isolate your cap, it will discharge on it's own anyway, they don't hold forever like a battery. All you need is a small resistor to "slow charge" your cap up to near battery level when reconnecting the battery. Simply touch one end of the resistor to the bat post, and the other end to the bat cable for minute or so. The cap will still charge up, but the resistor will limit the current. I use a 100 Ohm 10W. With this value, the current will never exceed 1A - 1.4A depending on the level of the battery. > I have a small .5 farad cap left over from a small sub I took out of > my old Honda. I want to add a small sub and this cap into another car. [quoted text clipped - 5 lines] > inaccessable area (behind a plastic side panel). Can anyone help me > with this? |
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